Pilosocereus is a genus of around 50 species of columnar cactis that spreads from Mexico and West Indies down to northern South America. They are mostly large columnar cacti. The name Pilosocereus comes from the Latine for 'hairy Cereus'.
As many other Cereus related cacti, Pilosocereus have large, light colored, heavily scented, funnel shaped flowers that open at night and stay open for less than 24 hours.
Pilosocereus are generally not frost resistant, and should be protected. If one of your specimen is outside and a light frost might occur, the usual way to protect it in Phoenix is to stick a polystyrene cup at the top of each stem. This added protection is enough to avoid damage to the frost tender growing point, and it can be left for several weeks without any damage to the tree.
Most Pilosocereus come from an area that has a marked dry season from November to May, and a wet season from May to October. In cultivation, they will generally enjoy regular watering and fertilizing in late spring to early autumn, while only light watering is needed the rest of the year.